^ Yes, and
Since you are using a 64 bit OS:
One check your BIOS to verify that it shows up in bios and if it does then to see if there is a setting for using 4 gigs
Two, if it does not show up in bios, try reseating memory modules.
hewelett packerd 785g6 vo 1.03
amd Athlon ll*2 215 socket am3 (938)